Wheelchairs are well known transportation appliances enabling the infirm, disabled and unwell person to move about with greater mobility than otherwise. Essentially, wheelchairs are small, single person conveyances typified by a chair supported by two outer, large diameter drive wheels behind the center of gravity of the user, and with two smaller swivel mounted wheels or castors located toward the front. Motive power may be supplied by an attendant pushing the wheelchair, by the user's hands and arms applied to the drive wheels, or by an auxiliary power source. The drive wheels may be cambered so that the distance between the two wheels at ground level is greater than the distance between the wheels at seating level. The camber angle provides stability for the wheelchair, and the inward tilt to the wheels at chair level enables the user to propel the chair more comfortably with the arms closer to the body.
While wheelchairs following many different designs have proliferated, there have been drawbacks heretofore that remain to be solved. In order to meet the needs and demands of the physically handicapped user, wheelchairs must be versatile and easily and readily adapted to accommodate the particular body shape and size of the user. Wheelchairs must also be versatile in adapting to both ambulatory and recreational travel, and they must be sufficiently rugged and durable to provide comfortable passage over uneven and irregular surfaces.
For instance, an unsolved need has arisen for a precise and convenient method for adjusting the camber angle of the wheels of the wheelchair in accordance with the various purposes for which the wheelchair is to be used. The camber angle may be adjusted from approximately 0 to 15 degrees and the stability generally increases as the camber angle increases. In addition, cambered wheels provide stability as the wheelchair is turned about a corner thereby helping to prevent the chair from tipping over. The camber angle for normal usage is approximately 3 degrees, while sports activities require greater camber angles for stability. For instance, camber angles for wheelchair basketball are typically 6 degrees, and camber angles for wheelchair tennis are typically 9 degrees.
A heretofore unsolved problem resulting from the camber angle of the wheels has been the inability of cambered wheelchairs to fit through narrow passageways. In addition, changing the camber angle has been time consuming, has required difficult mechanical, trial and error adjustments, and has resulted in undesirable changes in the wheelbase alignment of the castor wheels relative to the ground and the drive wheel base. Another unsolved need has been for a method for preselecting preset camber angles for specific user activities. Yet another unsolved need has been to provide a method for easily setting a camber angle without changing the wheelbase of the wheelchair.
Yet another unsolved need has been for a camber adjustment method for a modular wheelchair which may be customized to the needs of a particular patient by a therapist with simple adjustments without special skills, tools or training.